Amplifier system



Dec. 1I, 1934.

AMPLIFIER SYSTEM Filed Feb. 2, 1929 @5%. 'www B. F. MvlEssNER 1,983,802

Patented Dec. 11, 1934 UNlTED STATES 1,983,802 AMPLIFIER SYSTEM'.

Benjamin F. Miessner, Short by mesne assignments, to Radio America, New York,

Delaware Application February 2,

16 Claims.

The present invention relates to signal and like current amplifying systems, and particularly those employing thermionic amplifier devices. More particularly it relates to amplifier systems employing three electrode vacuum tube amplifiers energized from sources capable of introducing disturbing effects, such as hum, in the translating devices usually associated with amplifier systems,

An object of the invention is to economize in the amount of filter material going to make up the lter system interposed between the source of unsteady energy and the electrodes of the tubes energized therefrom by not endeavo-ring to obtain a complete or very high order of suppression of the unsteady or ripple component of the energy, but relying instead upon controlling the effects of the ripple component of the current without disturbing the useful amplifying characteristics of the system. To this end I make use of special features for opposing the ripple component arising in one part of the system by the ripple component arising in another part of the system, and controlling the magnitude and phase of these opposing components.

1n my copending application Serial No. 251,897 of February 4, 1928, now Patent 1,806,813 issued May 26, 1931, 1 show one form of hum neutralizing arrangement in an amplifying and reproducing system. The present invention is an improvement over said arrangement with features additional thereto, particularly in the matter of avoiding interference with amplification of signal currents.

The features of the present invention will be more fully understood by reference to the figures of the accompanying drawing in which like reference characters represent like parts so far as possible.

Fig. l is a stage of three diagrammatic showing of a single electrode vacuum tube amplification including the features of my invention.

Fig. 2 illustrates a modied form of my invention employed in a modified form of a stage of amplification.

Referring to Fig. 1 a three electrode vacuum tube VT has an input circuit including an input transformer Ti and an output circu't including an output transformer T2. The tube and circuits may be, for example, the last stage of a multi-stage cascade connected amplifier. The electrodes of the tube are shown energized from an alternating current source through primary winding P of transformer T, such as a commercial (S0-cycle lighting system. Secondary windings Si,

Hills, N. J., assignor, Corporation of N. Y., a corporation of 1929, Serial No. 337,148

S2 and S3 provide for heating the tube the filament of a rectier tube RT, and supplying current for rectification respectively, the rectified current being delivered to a filter system comprising filter condensers C3 and Ci and filter inductance L, thepositive and negative terminals of the filter being as indicated. The negative terminal is shown grounded at G, as to a metallic support or housing for the'organization of apparatus.

The .positive terminalof the filter is connected to the plate electrode of the tube through primary of output transformer T2, and the negative terminal of the filter is connected to the filament by way of ground G, vgrounded resistor Ri vand potentiometer K. Resistor Ri is chosen of such value that the plate current flowing therethrough develops the desired amount of potential for negatively biasing the grid by way of the grounded connection of the grid circuit through resistance R2.

I show a condenser Ci connected between the filament and plate circuit of the tube, which condenser has sufficiently low impedance to the currents being amplified tobypass degree these currents from the filter system and grid bias resistor Ri. doing feed back effects between input circuits of tube VT is to large inated, thus permitting the current amplification in the tube to be substantially normal. The by-passing of the signal current away from the filter system prevents developing signal voltages therein which could couple with other tubes or parts of a multi-stage system having other tubes supplied from the same filter, which coupling, because of the large amplification factor that may exist between removed stages of amplification, may cause serious undesired regenerative or degenerative eects. Furthermore, the removal of the resistor R1 from the signal current path eliminates signal energy loss therein, leaving more signal energy available to the output device.

1n my prior patent application referred to I showed a condenser connected in' similar manner but for the purpose of increasof ripple current from the filter flowing through bias producing resistor R1 in order to control the rippling potential on the grid in a way to control hum elimination by grid neutralization. A condenser of suitable capacity for this purpose is not in general of sufficiently large capacity for audio frequency signal current bypassing, so that a by-pass condenser adequate in filament,

the position of C1, and for its purpose in this application would permit too much ripple current to pass through bias resistor R1 if this condenser Were in the position referred to in my copending application, thus producing an excessive ripple voltage on the grid resulting in an undesirable degree of hum in the reproducer.

To permit of using an adequately large capacity condenser for signal current by-passing Without producing excessive hum, I make a circuit conthe plate and grid circuits including a condenser C2,

veloping in resistance R2 a ripple potential applied to the grid of phase opposed to the ripple potential applied to the grid from resistance R1, so that its excess potential may be neutralized. By choosing the values of condenser C2 and resistance R2 of proper amounts the ripple on the grid can be controlled in any desired way. It can be completely neutralized, or an excess of either phase can be left by over or under neutralizing. An excess may be desirable in many cases, as when it is desired to oppose hum currents arising in preceding stages of a multi-stage amplifier, or when it is desired to pass some residual hum current from the output of the tube to neutralize hum current in succeeding stages of amplincation or in a sound reproducer as, for example, a socalleddynamic reproducer having its eld energized by the nlter current.

For complete neutralization condenser C2 and resistance R2 may have the saine values as concomplete neutralization can be had when the values differ, but condenser C2 must be large when resistance R2 is small and vice versa. If con- Rz are made variable and adjusted not only can control be had over VT by alternating the plate current The frequency of the hum developed by the filament, when energized by 60 cycle alternating current, is predominantly 129 cycles, as is Well known.

The frequency of the hum developed by the other tWcsources is dependent upon the character of the rectifier tube RT. If of the half wave type the frequency is predominantly 60 cycle for RT is of the full wave the frequency is predominantly the grid circuit to neutralize the hum produced by the fluctuating potential energization of the grid,

Thus in the present application the adjustments provided and described permit utilizing the hum arising in the plate circuit, i. e. the B hum,

grid circuit, C hum, and also the num produced by the alterhating current energization of the filament, i. e. the A hum.

In the arrangement of Fig. 2 the details of the supply and lter system are omitted, the terminals of the nlter being indicated by terminals B- and B+. In this figure I show What is termed a condenser ducer device rents are choked by L1 direct to the filament by and reproducer LS, and thus avoid in large measure feed back effects.

tional pulsating current, one terminal of Which is connected to the plate of said tube, and the other terminal pulsations from said source across said resistance, connections between said grid-lament circuit and said resistance whereby the average potential of said grid is maintained at a known value relative to that ci said filament, and means for impressing on said grid pulsations from said source of a phase of said excess pulsations.

2. In a signal current amplifying system including an amplifier tube having grid-filament and plate-lanient circuits, a resistance, a source of uni-directional pulsating current, one terminal of which is connected to the plate of said tube and the other terminal of Which is connected through a portion of said resistance tothe filament of said tube, said grid-lament circuit including said resistance, whereby the average potential of said tube, said grid-filament circuit including said resistance, whereby the average potential of said grid is maintained at a known value relative to that of said filament, means for impressing in predetermined degrees excess pulsations from said source across said portion of said resistance and means ior impressing on said grid pulsations from said source of a phase-opposite to that of said excess pulsations, said means consisting of a variable condenser connected between said gridfilament circuit and a point within said platefilament circuit between said source and said plate.

4. In a signal current ampliiier system including an ampliiier tube having grid-iilament and plate-filament circuits, a source o uni-directional pulsating current, one terminal of which is connected to the plate of said tube, and the other terminal of which is connected through a resistance to the iilament of said tube, a connection for impressing the potential developed in said resistance upon the grid of said tube, a signal current by-pass condenser shunting a portion of said plate-filament circuit whereby excess pulsations from said source are passed through said resistance, and means for impressing upon the grid of said tube pulsations from said source of phase opposed to said excess pulsations. f`

5. in a signal current amplifier system including a three-electrode vacuum tube having an input circuit and an output circuit including an inductive device, a source of uni-directional pulsating current, one terminal of which is connected to the plate oi said tube through said inductive device and the other terminal of which is connected through a potential developing impedance to the filament of said tube, a connection for impressing the potential developed in said impedance upon the grid of said tube, a signal current by-pass condenser connected between said inductive device and said lament, whereby excess pulsations from said. source pass through said impedance and means for impressing pulsations from said source upon the grid of said tube oi phase opposed to said excess pulsations.

6. ln a signal current amplifier system including a three-electrode vacuum tube having an input circuit and an output circuit including an inductive device, a source or" uni-directional pulsating current, one terminal of which is connected to the plate of said tube through'said inductive device and the other terminal oi which is connected through a potential developing impedance to the iilament oi said tube, a connection for impressing the potential developed in said impedance upon the grid of said tube, a signal current by-pass condenser connected between said inductive device and said filament, whereby excess pulsations from said source pass through said impedance and means for impressing pulsations from said source upon the grid of said tube of phase opposed to said excess pulsations, said means including a variable condenser connected between said source-connected terminal of said inductive device and said grid filament circuit.

7. In a signal current amplifier system including a three-electrode vacuum tube having an input circuit and an output circuit including an inductive device, a source or uni-directional pulsating current, one terminal of which is connected to the plate of said tube through said inductive device and the other terminal of which isv connected through a potential developing impedance to the filament of said tube, a connection for impressing the potential developed in said impedance upon the grid of said tube, a signal current by-pass condenser connected between said inductive device and said iilament, whereby excess pulsations from said source pass through said impedance and means for impressing pulsations from .said source upon the grid of said tube of phase opposed to said excess pulsations, said means comprising a condenser and a second inductive device connected between said sourceconnected terminal of said first-mentioned inductive device and said grid-filament circuit of said tube.

8. In a signal current amplifier system including a three-electrode vacuum tube having an input circuit and an output circuit including an inductive device, a source of uni-directional pulsating current, one terminal of which is connected to the plate of said tube through said inductive device and the other terminal of which is connected through a potential developing impedance to the filament of said tube, a connection for impressing the potential developed in said impedance upon the grid of said tube, a signal current by-pass condenser connected between said inductive device and said filament, whereby excess pulsations from said source pass through said impedance and means for impressing pulsations from said source upon the grid or" said tube of phase opposed to said excess pulsations, said means comprising a condenser and a second inductive device connected between said sourceconnected terminal of said first-mentioned inductive device and said grid-iilament circuit of said tube, said inductive devices having substantially identical electrical characteristics whereby the fluctuation oi space current in said tube is controlled.

9. In an amplifier system including an amplifying tube having grid-iilament and plate-niament circuits and a source ol power for said platefilament circuit, the potential of which is irregular, the combination of a connection between one terminal o said source and the plate oi said tube, said connection including a choke coil, a plurality of resistances connected between said grid and said ilament, a connection between the other terminal ci said source and a point between said resistances, an indicator and a capacity series connected between the plate terminal oi said choke coil and said filament, and a capacity connection between the source terminal of said choke coil and the grid of said tube, whereby the fluctuation oi the space current of said tube is controlled.

l0. In an amplier system including an amplifier tube having grid-filament and plate-iilament circuits and a source of power lor said plate i'ilament circuit, the potential of which is irregular, the combination of a connection between one terminal oi said source and the plate of said tube, said connection including a choke coil, a plurality of resistances connected between said grid and said filament, a connection between they other terminal of said source and a point'between said resistances, an inductive indicator and a capacity series connected between the plate terminal of said choke coil and said filament, and a capacity connection between the source terminal of said choke coil and the grid of said tube, said capacity connection including a phase modifying inductance whereby the fluctuation of the space current of said tube is controlled.

1l. The method of energizing an amplifier system including an electron tube having A, B and C circuits, which consists in energizing the A circuit with alternating current, and energizing maintained at to neutralize the hum produced by the current energization of the A circuit.

l2. The method of energizing an amplifier alternating current and' regulating the phase and amplitude of the fluctuating component of said fluctuating current applied to said B and C anode to the grid and a resistance connected from the grid side of said last-named capacity to the negative terminal of said source, for compensating the excess current fed by said path.

14. In a signal current amplifying system comprising an amplier tube having grid-cathode and anode-cathode circuits, a source of uni-directional pulsating current and a resistance in series therewith forming part of said anodecathode circuit, said resistance being also included in the grid-cathode circuit of said tube, whereby the average potential of said grid is a known value relative to that of the cathode, a path or" low impedance to be ampliiied across said source and said resistance for forming a by-pass circuit for said signal currents around the source of pulsating current and said resistance whereby feedback effects between the output and input circuits of said tube are substantially eliminated, said path causing an excess iiow of pulsating current through said resistance thereby producing an excessive ripple voltage on the grid and an undesirable degree of hum in the output circuit, and means comprising a capacity and a resistance forming a series circuit shunted across said source and a connection between a point common to said resistance and said capacity and the grid for producing compensating effects with respect to the excess current.

15. In a signal current amplifying system an amplier tube having grid-cathode and anodeaverage potential of the grid-electrode with respect to the cathode is maintained at a known value, a path of low impedance to signal energy input circuits of said tube are substantially eliminated, the impedance of said path being inherently low for the ductuating current components of energy from said source whereby excesiiuctuating components by-passed resistance impedance element in the gud-cathode path and means for impressing across said impedance eleand magnitude to compensate said excess iluctuating components.

16. In a signal current amplifying an amplier tube having an anode, a cathode and a control the auxiliary resistor and the bias resistor in series, a connection between the anode and cathode electrodes of said tube including a capacity having low impedance to signal currents to by-pass the signal currents from said source and the bias resistor, said capacity and said bias resistor forming a shunt circuit across said source of uni-directional current whereby alternating current components from said source are by-passed through said bias resistor, a capacity shunted from said anode to the grid side of said auxiliary resistor, said second capacity and auxiliary resistor also forming a circuit shunted across the source of uni-directional current whereby hum BENJAMIN F. M'IESSNER. 

